Cavity resonator devices



Feb. 12, 1957 B. B. CORK ET AL CAVITY RESONATOR DEVICES 3 Sheets-Sheet 1Filed Dec. 2'7, 1945 awe/Whom BRUCE B. CORK MELVILLE' CLARK JR.

Feb. 12, 1957 B. B. CORK EIAL CAVITY RESONATOR DEVICES s Sheets-Sheet 2Filed Dec. 27, 1945 BRUCE- a. CORK MELVILLE CLARK JR.

3 Sheets-Sheet 3 BRUCE- B. CORK MELVILLE CLARK JR.

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substantially detune that portion of the cavity so that only a smallportion of the transmitter energy will be coupled to conductor 27 andthence to the I. F. post 35 and local oscillator 41. The I. F. crystalwill thus be protected from burning out at the high level of thetransmitter energy.

Energy received by the antenna, when the transmitter is not inoperation, will be applied to the cavity through post 15. Some energywill be coupled through iris 14 to the transmitter oscillator but thiswill be small because the transmitter, when not energized, will bedetuned from the frequency of the incoming energy.

Accordingly the greater part of the energy will be coupled from post 15to conductor 21. Conductors 21 and 27, comprising double-tuned resonantcircuit, will pass the energy with minimum attenuation to the I. F.coupling post 35, where it will be mixed with local oscillator energycoupled through iris 37 and taken out of the cavity for application toan intermediate frequency detector.

If it is desired to operate the transmit-receive assembly in a difierentfrequency range, tuning rod 34 may be moved to alter the position alongthe frequency spectrum of the mid-point of the pass band of thedoubletuned resonant circuit comprising conductors 21 and 27.

In order to adjust the circuit so that the tuning of line 27 will havethe desired relation to that of line 21, a hollow screw 42 may beinserted immediately below the end of conductor 27, forming a variablecapacitive load, which may be adjusted until proper operatingcharacteristics are obtained.

When the equipment is not in use, the keep-alive voltage will be shutoff from the TR tube 22. Under such circumstances, if high level energyshould be received by the antenna and applied to coupling post 15, itmight be transmitted through the TR to coupling post 35 damaging the I.F. detector and/or local oscillator. Under such conditions, a conductingrod 43 may be slid within hollow screw 42 until it touches the end ofconductor 27. This portion of the cavity will then be short-circuited,constituting to an augmented extent, the same type of protection as isprovided during operation by the TR tube 22.

The assembly shown in Figs. 2, 3, and 4 is substantially the same asshown in Fig. 1 with the following modifications. In the first place, aspecial tuning means has been. The.

shown for actuating the tuning rod 34 of Fig. 1. action of this tuningmeans will be quite obvious by reference to Fig. 2. Additionally, tuningslugs 31 and 32, shown as homogeneous conducting members in Fig. 1, havebeen replaced by a single, integral non-conductive member 50 attached inthe center to tuning rod 34. At high frequency, current is confined tothe surface of a conductor, and it is possible to use a slug in the formof a toroid of non-conductive material coated with a conductive materialsuch as silver. In Fig. 2, tuning member 50 comprises a pair of toroidsof non-conductive matter coated with a layer of silver as shown at 51.

With these exceptions the assembly of Figs. 2, 3 and 4 is substantiallythe same as that of Fig. 1, and the same reference numerals have beenapplied to corresponding parts.

It has been found that conducting wall 30 of Fig. 1 may be replaced by ascrew 60 (Fig. 5) extending upward into the cavity from floor 13. Byproper proportioning the screw, it has been found that the desiredcoupling may be maintained, and at the same time a certain degree ofdiscrimination against an undesired harmonic, such as the thirdharmonic, may be obtained. If desired, coupling screw 60 may extendinward from either wall or wall 11, instead of upward from floor 13.Also, under certain conditions a plurality of screws may be substitutedfor wall 30 of Fig. 1.

While the coupling between the several members within the cavity hasbeen shown as a large iris, equal to the cross section of the cavity, itwill be understood that, if desired, the coupling between members may bevaried by use of a wall such as wall 30, or by coupling screws such asscrew 60, or by use of a small iris such as iris 37.

It will be further understood that this invention is not limited to iriscoupling between the portions of the circuit; loop coupling orcapacitive coupling may be employed where appropriate.

It will be further understood that any form of transmitter, localoscillator, I. F. detector or antenna may be employed in connection withthe transmit-receive assembly of this invention.

Although we have shown and described certain specific embodiments of theinvention, we are fully aware of the many modifications possiblethereof. This invention is not to be restricted except insofar as isnecessitated by prior art and the spirit of the disclosure.

What is claimed is:

l. A double-tuned resonant circuit comprising a plurality of conductingwalls forming a cavity, a first elongated conductor connected at one endto a first cavity wall and extending into the cavity, a second elongatedconductor connected at one end to said first cavity wall and extendinginto the cavity, an intermediate conductor connected to a cavity wallopposite said first cavity wall and extending into the cavity betweensaid first and said second elongated conductors, a pair of conductingtuning slugs positioned about said first and said second elongatedconductor-s respectively and movable along the respective axes of saidconductors, and adjustable positioning means attached to said tuningslugs and extending through a wall of the cavity to provide simultaneouadjustment of the position of said tuning slugs.

2. A transmit-receive device comprising a plurality of conducting wallsforming a cavity resonator, a first elongated conductor connected to awall of the cavity and extending into the cavity, input means adjacentsaid first elongated conductor eifective to apply input energy to saidcavity, a second elongated conductor adjacent to said first conductorand connected to said wall of said cavity and extending into the cavity,output means adjacent said second conductor effective to derive outputenergy from said cavity, a nonlinear impedance connected between one ofsaid conductorsat its end extending into the cavity and the adjacentcavity wall effective to change abruptly in impedance value uponapplication of high voltage energy thereto,, conducting means connectedto one of said cavity walls and between said elongated conductors andextending into said cavity toward an opposite wall for a portion of thedistance between said two last-mentioned cavity walls, a pair ofconducting tuning slugs positioned about said first and said secondelongated conductors respectively and movable along the respective axesof said conductors, and an adjustable positioning means attached to saidtuning slugs and extending through a wall of said cavity to providesimultaneous adjustment of the position of said tuning slugs.

References Cited in the file of this patent

